Mitigation of Jahn-Teller distortion and Na+/vacancy ordering in a distorted manganese oxide cathode material by Li substitution

Layered manganese-based oxides are promising candidates as cathode materials for sodium-ion batteries (SIBs) due to their low cost and high specific capacity. However, the Jahn-Teller distortion from high-spin Mn3+ induces detrimental lattice strain and severe structural degradation during sodiation and desodiation. Herein, lithium is introduced to partially substitute manganese ions to form distorted P ' 2-Na0.67Li0.05Mn0.95O2, which leads to restrained anisotropic change of Mn-O bond lengths and reinforced bond strength in the [MnO6] octahedra by mitigation of Jahn-Teller distortion and contraction of MnO2 layers. This ensures the structural stability during charge and discharge of P ' 2-Na0.67Li0.05Mn0.95O2 and Na+/vacancy disordering for facile Na+ diffusion in the Na layers with a low activation energy barrier of similar to 0.53 eV. It exhibits a high specific capacity of 192.2 mA h g(-1), good cycling stability (90.3% capacity retention after 100 cycles) and superior rate capability (118.5 mA h g(-1) at 1.0 A g(-1)), as well as smooth charge/discharge profiles. This strategy is effective to tune the crystal structure of layered oxide cathodes for SIBs with high performance.

Automated summary

Introducing lithium ions to partially substitute manganese ions in layered manganese-based oxides leads to a distorted structure which enhances the performance of cathode materials in sodium-ion batteries. This strategy improves specific capacity, cycling stability, and rate capability in SIBs.